5 replies to this topic

[Ian]

Just put in a new rebuilt starboard motor rotax 787 from SBT. Now motor is not getting spark. Any suggestions where should I start diagnostic... Not really familiar with ignition system with this motors..

Thanks

[Ian]

Oops by the way, my port motor does get sparks and runs.

[Kevin Leclair]

This one would be a little tough to diagnose remotely, have you called SBT to see what they might be able to suggest?

[Rave1]

Soo has the spark problem been remedied,Ground problems maybe?

[Ian]

Sorry guys! I've been busy working and now finally got spark, fixed timing too... I took my boat out couple days ago to break in my new motor... Everything was running well...All of a sudden when I was running the boat at about 4k rpm and drop it down to just put put, both motor died.... trying to start her back up and all i got was a click.. seam like the battery was dead... so i drifted for about ten minutes and decided to start her just for the heck of it to see maybe i have enough juice on the battery..... My new motor started barely and my old motor would only click... Now maybe is the starter solenoid or something...Anyways got back to the house and decided to charge my battery.... next day ! battery was fully charge... I wanted to try again and old motor was cranking but seem week.... So took out the plugs and check for compression and cylinder close to magneto was only 10psi and the other was 100psi.....

Do you guys think that my piston and rings needs a rebuilt...This old motor was reading at 130psi before i went out....

What steps should I do to see if its really my rings and pistions....

Thanks

[adventurer]

Sorry guys! I've been busy working and now finally got spark, fixed timing too... I took my boat out couple days ago to break in my new motor... Everything was running well...All of a sudden when I was running the boat at about 4k rpm and drop it down to just put put, both motor died.... trying to start her back up and all i got was a click.. seam like the battery was dead... so i drifted for about ten minutes and decided to start her just for the heck of it to see maybe i have enough juice on the battery..... My new motor started barely and my old motor would only click... Now maybe is the starter solenoid or something...Anyways got back to the house and decided to charge my battery.... next day ! battery was fully charge... I wanted to try again and old motor was cranking but seem week.... So took out the plugs and check for compression and cylinder close to magneto was only 10psi and the other was 100psi.....

Do you guys think that my piston and rings needs a rebuilt...This old motor was reading at 130psi before i went out....

What steps should I do to see if its really my rings and pistions....

Thanks

Hi there!!

well I will start by removing the cylinder head, look at the chamber of the cylinder with no compression to see any partycle damage, if particle damage is found then the problem is more serious as the crankshaft maybe damaged. when the bearing at the connecting rod breaks the particles run up to the head chambers and betwen the piston and cylinder wall, manually rotate the cranckshaft to look for scratches on the cylinder wall. if the cylinders are scratched you may need to install a new crankshaft,pistons and bore your cylinders to the next piston size. in other words overhaul the engine. if after inspecting it the cranckshaft is ok then the engine may have overheated and the piston got stuck in the cylinder due to expansion, in this case you need new pistons and if the cylinder is scratched you also need to bore it to the next size.

good luck and keep it posted!!